Specifications

66
Compressor Safeties — The 48/50A series units with
the ComfortLink™ Controls include a compressor protection
board (CSB) that protects the operation of the compressors.
The board senses the presence or absence of current to each
compressor. If there is a command for a compressor to run and
there is no current, then one of the following safeties or condi-
tions have turned the compressor off.
• Compressor overcurrent — smaller compressors have inter-
nal line breaks and larger compressors have a dedicated
circuit breaker for over current protection.
• Compressor short circuit — If the compressor circuit
breaker that provides short circuit protection has tripped
then there will be not current.
• Compressor motor over temperature — If the internal
line-break or over temperature switch has opened.
• High-pressure switch trip
Alarms will also occur if the current sensor board malfunc-
tions or is not properly connected to its assigned digital input.
If the compressor is commanded OFF and the Current
Sensor reads ON, an alert is generated. This will indicate that a
compressor contactor has failed closed. In this case a special
mode “Compressor Stuck on Control” will be enabled and all
other compressors will be turned off and an alarm enabled to
indicate that service is required.
Any time the alert occurs, a strike is called out on the affect-
ed compressor. If three successive strikes occur the compressor
will be locked out requiring a manual reset or power reset of
the circuit board.
The clearing of strikes during compressor operation is a
combination of 3 complete cycles or 15 continuous minutes of
run time operation. If there are one or two strikes on the com-
pressor and three short cycles (ON-OFF, ON-OFF, ON-OFF)
less than 15 minutes each occur, the strikes are reset to zero for
the affected compressor. If the compressor turns on and runs
for 15 minutes straight with no compressor failure, the com-
pressor strikes are cleared.
Time Delay Safety Limits — The control will not allow
any output relay to come on within 3 seconds of any other
output relay.
For outputs connected to the compressors, the control will
use a Compressor Minimum OFF Time of 2 minutes, a
Compressor Minimum ON Time of 3 minutes and a Minimum
Delay before turning on second compressor of 10 seconds.
Heat stages require no time-guard protection but will be
managed appropriately by the staging routines.
Demand Limiting — The term Demand Limit Control
refers to the restriction of the machine capacity to control the
amount of power that a machine will use. Demand limit control
is intended to interface with an external Loadshed Device
either through CCN communications, external switches, or 4 to
20 mA input.
The ComfortLink control has the capability of Load shed-
ding and limiting in 3 different ways:
• Two discrete inputs tied to configurable demand limit set
point percentages.
• An external 4 to 20 mA input that can reset capacity back
linearly to a set point percentage.
• CCN loadshed POC (product outboard control) functionality.
To use Demand Limiting, select the type of demand limiting
to use. Then configure the Demand Limit set points based on
the type selected. The configurable set points can be found in
the CONFIGURATION-DMD.L submenu. To disable Demand
Limiting set the DMLS configuration to no demand limiting.
To use Demand Limiting select the type of demand limiting to
use. This is done using the Demand Limit Switch Select
(DM.L.S) variable located in the CONFIGURATION-DMD.L
submenu. The following options are available:
• (0) NO DEMAND LIMIT — This will disable the use of all
demand limits.
• (1) SWITCH — This will enable the switch input demand
limit using the switch inputs connected the CEM board.
Connections should be made to TB6 terminals 4, 5, and 6.
• (2) 4-20MA — This will enable the use of a remote 4 to
20 mA demand limit signal. The CEM module must be
used. The 4 to 20mA signal must come from an externally
sourced controller and should be connected to TB6 termi-
nals 9 and 10.
• (3) CCN LOADSHED — This will allow for loadsheding
through CCN communications.
SWITCH DEMAND LIMIT — If the unit has been config-
uredforSwitchdemandlimitingbysettingtheDM.L.Svari-
able to Switch, then the External Demand limit switch 1
(DLM.1) and External Demand Limit Switch 2 (DLM.2) will
be used. The status of these switch inputs can be view using the
INPUT-SW.IN submenu. The amount of demand limiting asso-
ciated with each switch closure can be configured using the
Demand Limit SW.1 Setpt (DLS.1) and Demand Limit SW.2
Setpt (DLS.2). These can be set using the CONFIGURATION-
DMD.L submenu. Setting is the maximum % capacity that will
be allowed when the switch is closed.
Closing the first stage demand limit contact will limit the
mechanical cooling capacity of the unit to the first demand
limit level (DLM.1). The unit will not exceed the percentage of
capacity entered as the Demand Limit Switch 1 set point
(DLM.1). Closing the contacts on the second demand limit
switch (DLS.2) prevents the unit from exceeding the capacity
entered as Demand Limit Switch 2 set point (DLM.2). The
Demand Limit stage set to the lowest demand takes priority if
both demand limit inputs are closed. If the demand limit
percentage does not match unit staging, then the unit will limit
capacity to the closest capacity stage.
To allow for interface with different control systems the
switches can be configured as normally open or closed
using the following configurations that are located in the
CONFIGURATION-SW.LG submenu.
DMD.LMT.SW.1 Normally: (DM.1.L)
— This sets the nor-
mally open and closed status of the switch.
DMD.LMT.SW.2 Normally (DM.2.L)
— This sets the nor-
mally open and closed status of the switch.
EXTERNALLY POWERED 4 TO 20 MA DEMAND — To
configure Demand Limit for 4 to 20 mA control, set the
Demand Limit Select (DM.L.S) to 4 to 20 mA. Configure the
Demand Limit at 20 mA (DL20) to the maximum loadshed
value desired. The control will reduce allowable capacity to
this level when the input signal (DM.AI) is at 20 mA. The
DM.AI input can be found in the INPUT-MISC submenu.
When the signal is 4 mA, 100% capacity will be allowed. For a
signal between 4 mA and 20 mA, a linear limiting equation
will be used.
CCN LOADSHED DEMAND LIMIT — To configure De-
mand Limit for CCN Loadshed control, set the Demand Limit
Select (DM.L.S) to CCN loadshed. Configure the Loadshed
Group Number (LSGN), Loadshed Demand Delta (LSDD),
and Maximum Loadshed Time (LSTM). These set points are in
the CONFIGURATION-DMD.L submenu.
The Loadshed Group number is established by the CCN sys-
tem designer. The MBB will respond to a Redline command
from the Loadshed control. When the Redline command is
received, the current stage of capacity is set to the maximum
stages available. Should the loadshed control send a Loadshed
command, the MBB will reduce the current stages by the value
entered for Loadshed Demand delta. The Maximum Loadshed
Time defines the maximum length of time that a loadshed con-
dition is allowed to exist. The control will disable the Redline/
Loadshed command if no Cancel command has been received
within the configured maximum loadshed time limit.